scholarly journals Determination of the Downwelling Diffuse Attenuation Coefficient of Lake Water with the Sentinel-3A OLCI

2017 ◽  
Vol 9 (12) ◽  
pp. 1246 ◽  
Author(s):  
Ming Shen ◽  
Hongtao Duan ◽  
Zhigang Cao ◽  
Kun Xue ◽  
Steven Loiselle ◽  
...  
Keyword(s):  
Attenuation Coefficient ◽  
Lake Water ◽  
Diffuse Attenuation Coefficient

scholarly journals Diurnal Variation of the Diffuse Attenuation Coefficient for Downwelling Irradiance at 490 nm in Coastal East China Sea

2021 ◽  
Vol 13 (9) ◽  
pp. 1676
Author(s):  
Yu Zhang ◽  
Zhantang Xu ◽  
Yuezhong Yang ◽  
Guifen Wang ◽  
Wen Zhou ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Attenuation Coefficient ◽  
East China Sea ◽  
East China ◽  
Coefficient Of Determination ◽  
Target Area ◽  
Diffuse Attenuation Coefficient ◽  
China Sea ◽  
Mean Square Errors ◽  
Downwelling Irradiance

The diurnal variation of the diffuse attenuation coefficient for downwelling irradiance at 490 nm (Kd(490)) has complex characteristics in the coastal regions. However, owing to the scarcity of in situ data, our knowledge on the diurnal variation is inadequate. In this study, an optical-buoy dataset was used to investigate the diurnal variation of Kd(490) in the coastal East China Sea, and to evaluate the Kd(490) L2 products of geostationary ocean color imager (GOCI), as well as the performance of six empirical algorithms for Kd(490) estimation in the Case-2 water. The results of validation show that there was high uncertainty in GOCI L2 Kd(490), with mean absolute percentage errors (MAPEs) of 69.57% and 68.86% and root mean square errors (RMSEs) of 0.70 and 0.71 m−1 compared to buoy-measured Kd12(490) and Kd13(490), respectively. Meanwhile, with the coefficient of determination (R2) of 0.71, as well as the lowest MAPE of 27.31% and RMSE of 0.29 m−1, the new dual ratio algorithm (NDRA) performed the best in estimating Kd(490) in the target area, among the six algorithms. Further, four main types of Kd(490) diurnal variation were found from buoy data, showing different variabilities compared to the area closer to the shore. One typical diurnal variation pattern showed that Kd(490) decreased at flood tide and increased at ebb tide, which was confirmed by GOCI images through the use of NDRA. Hydrometeorological factors influencing the diurnal variations of Kd(490) were also studied. In addition to verifying the predominant impact of tide, we found that the dominant effect of tide and wind on the water column is intensifying sediment resuspension, and the change of sediment transport produced by them are secondary to it.

Bioassay Method for the Determination of Toxaphene in Lake Water

1966 ◽  
Vol 23 (5) ◽  
pp. 723-727
Author(s):  
L. M. Royer
Keyword(s):  
Lake Water ◽  
Small Volume ◽  
Bioassay Method ◽  
Lebistes Reticulatus

A method based on static bioassays was developed to measure the concentration of toxaphene before restocking of lakes treated with this toxicant. A double distillation technique was used to extract the toxaphene and concentrate it in a small volume of distillate. Bioassays were then carried out in 200-ml samples of distillate reconstituted with electrolytes to match a standard water. Guppies, Lebistes reticulatus (Peters), less than 7 days old were used as test organisms.The method developed was used to follow the detoxification of Midway Lake which was rehabilitated with toxaphene. Data on the rate of detoxification are presented.

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